1. Field of the Invention
The present invention relates to an armrest apparatus for adjusting the angle of armrests used in automobiles, in welfare devices including, for instance, wheelchairs and in various fixed seats, so that the armrest is capable of making rotation from an initial horizontal position to a raised stowed position aligned with the seat back of the seat.
2. Description of the Related Art
An armrest must be restricted (locked) from rotating downward and allowed (unlocked) to rotate upward, and a coil spring is typically used for such a mechanism. Generally, if the coil spring is kept fastened to a certain extent to a drum and the other end is wound while left free, the coil spring remains tightened to the drum and cannot rotate by itself when the side at one end is turned in the direction that the coil spring tightens (diametrical reduction), and the coil spring rotates freely and smoothly over the drum when the side is turned in the direction that the coil spring loosens (diametrical expansion). Devices in which the angle of the armrest is adjusted by the coil spring utilize this property, and the resulting advantage is that the angle of the armrest can be adjusted in a stepless fashion.
However, this property is a hindrance when the armrest is returned to the initial position. At this time, it is necessary to prevent the coil spring from tightening; but in conventional structures, some kind of separate control member is provided, and the above-described property of the coil spring is counteracted by this control member when the armrest is returned to the initial position. This results in drawbacks in that both the armrest and the control member must be operated, and the operation becomes complex. In view of this, the inventors of the present applicant have proposed a mechanism in which the tightening and loosening of the coil spring is controlled by the armrest alone (see Japanese patent application No. 2004-238166).
However, in this prior art, the drum is fixed to the fixed member side (sheet); and this structure has problems. The width of the casing for fixing one end of the coil spring and housing the coil spring increases by a certain extent in order to ensure the number of turns of the coil spring, and the width of the armrest itself that is linked to the casing also increases accordingly. Therefore, installation is constrained in seat devices that do not have sufficient width.